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Renovate or knock down and rebuild? Cost calculator for Sydney (2026)

Compare the all-in cost of renovating your house, with or without an extension or second storey, against knocking it down and building new. Every rate comes from a published, dated 2026 source; the rebuild side uses the same rates as AUD Build’s knockdown rebuild calculator.

By XLGUpdated: 2026-10-28Every figure is dated and sourced

Short answer

A renovation usually costs less in total than a knockdown rebuild, but a major structural renovation with an extension or second storey can come close [7]. With this calculator, a mid-range renovation of a 180 m² house comes to about A$128k–A$257k, against about A$473k–A$786k to knock it down and rebuild the same size with a year’s rent: about 31% of the rebuild. A substantial renovation with a 40 m² extension comes to about 59% of a 220 m² custom rebuild. Some Sydney builders and quantity surveyors treat about 60–70% of the rebuild cost as the point where rebuilding starts to make more sense; it is a rule of thumb, not a standard [7] [8].

Calculate your estimate

Your house and the renovation

Floor area of the existing house (m²)

Renovation scope

Ground-floor extension (new m², 0 if none)

Second-storey addition (new m², 0 if none)

Renovation approval

Weeks out of the house during the renovation

The rebuild

Floor area of the new home (m²; usually the existing area plus any extension or second storey)

Location

New home specification

Rebuild approval

Weeks renting during the rebuild

Both options

Weekly rent (A$)

Your site Asbestos likely (built before 1987) The renovation moves a kitchen or bathroom Sloping block (adds retaining to the rebuild) Heritage item or heritage conservation area

Median weekly house rents, April–June 2026: Greater Sydney A$800, Blacktown A$700, The Hills A$900, Hornsby A$975, Ku-ring-gai A$1,400.

Your estimate

Renovation

Item	Range

Knockdown rebuild

Item	Range

Worked examples

Scenario	Renovation	Knockdown rebuild	Renovation as % of rebuild
180 m² house, mid-range renovation (CDC), asbestos, stay at home · or rebuild 180 m² project-spec in Western Sydney (CDC), 52 weeks’ rent at A$800	A$128k–A$257k	A$473k–A$786k	31%
180 m² house, substantial renovation plus 40 m² ground-floor extension (DA), asbestos, kitchen moved, 13 weeks out · or rebuild 220 m² custom mid-range in Western Sydney (DA), 52 weeks’ rent	A$351k–A$703k	A$682k–A$1.09m	59%
North Shore 200 m² house, mid-range renovation plus 100 m² second storey (DA), asbestos, 26 weeks out at A$1,400 · or rebuild 300 m² custom mid-range on a sloping block (DA), 52 weeks at A$1,400	A$465k–A$789k	A$1.32m–A$1.79m	40%

Rates and allowances used

Item	Range used	Basis	Source
Renovation of the existing house (floor area × scope rate) · Cosmetic (paint, floors, fixtures)	A$175–375/m²	Buildana’s A$35k–75k for a 200 m² house ÷ 200	[1]
Renovation of the existing house (floor area × scope rate) · Mid-range (kitchen, bathrooms, flooring, paint, minor structural)	A$675–1,225/m²	Buildana’s A$135k–245k for a 200 m² house ÷ 200	[1]
Renovation of the existing house (floor area × scope rate) · Substantial (new wet areas, structural alterations, rewiring, replumbing)	A$1,225–2,425/m²	Buildana’s A$245k–485k for a 200 m² house ÷ 200	[1]
Ground-floor extension (new m² × rate)	A$2,500–4,500/m²	Basic to premium extensions	[2]
Second-storey addition (new m² × rate)	A$2,800–4,500/m²	Basic to premium; Pearson gives A$3,000–4,500	[3] [4]
Approval: CDC	A$2k–6k	Renovation A$2k–5k; second storey A$3k–6k	[1] [4]
Approval: DA	A$3k–15k	Renovation A$3k–12k; second storey A$6k–15k	[1] [4]
Structural assessment and engineering	A$2k–5k	Substantial scope, extension or second storey	[1]
Asbestos testing and removal	A$3k–28k	From one room to a whole house	[1] [12]
Moving a kitchen or bathroom (plumbing and electrical)	A$8k–20k	If a wet area moves	[1]
HBC insurance (icare base rate 1.111% for work to an existing dwelling)	1.111%	Code H04, metro, including GST and stamp duty	[9] [11]
Long service levy (0.25% of works, if A$250,000 or more)	0.25%	Works of A$250,000 or more	[10]
Renovation contingency	10–15%	Shown separately	[5] [6]
Knockdown rebuild side	—	Same rates as the knockdown rebuild calculator; contingency 5–15%	[12]

How the estimate is built

Renovation = existing floor area × a scope rate, plus any extension or second storey × its per-m² range. The scope rates divide Buildana’s May 2026 ranges for a typical 200 m² house by 200; they are Western Sydney builder figures, and North Shore jobs often cost more (Pearson gives A$200,000–A$600,000 for a standard 3–4 bedroom whole-house renovation in the Hills and North Shore).
Approvals, structural assessment, asbestos, moving wet areas, HBC insurance and the long service levy are added from their published ranges. HBC uses icare’s rate for work to an existing dwelling; the levy applies only when the works reach A$250,000.
The rebuild side is the knockdown rebuild calculator: new floor area × rate, demolition, services, reports, design, approval, site works, external works, council contributions, the levy, HBC and rent.
The percentage compares the middle of each all-in range, before contingency. Renovation contingency is 10–15% (Pearson, MNA); rebuild contingency is 5–15%.
Not included: land, transfer duty (neither option triggers it on land you already own), pools, furniture, loan costs and changes in value. Design fees for a renovation are not itemised in the published ranges; ask whether each quote includes them.

Questions

Is it cheaper to renovate or knock down and rebuild in Sydney?

Usually renovating, in total cost. A rebuild can look similar per m², but demolition, a full new home and rent make the whole project dearer. A major structural renovation with an extension or second storey can approach the cost of a rebuild.

At what point does rebuilding make more sense than renovating?

Some Sydney builders and quantity surveyors use about 60–70% of the rebuild cost as a crossover: CPP Quantity Surveyors says about 60%, and Buildana’s calculator uses 60–65%. It is a rule of thumb, not a standard; the condition of the structure, heritage controls and what each option gives you matter as much.

Can I knock down a house in a heritage conservation area?

Not as complying development. In a heritage conservation area a CDC can only demolish minor parts, such as walls not facing the main road, outbuildings and internal elements, so demolishing the whole house needs development consent from council.

Does a renovation need BASIX?

Yes, if the alterations and additions are valued at A$50,000 or more. Renovations have minimum requirements rather than set energy and water targets; a new home must meet the full BASIX standards, including an average of 7 NatHERS stars.

How accurate is this calculator?

It gives a budgeting range for comparing two options, not a quote. Ask for a structural assessment of the existing house before you choose; hidden defects change the renovation figure most.